Monday, 29 June 2015

METALS AND NON – METALSElements are classified broadly into two categories on the basis of properties:Metals: Iron, Zinc, Copper, Aluminium etc.Non – metals: Chlorine, Nitrogen, Hydrogen, Oxygen, Sulphur etc.Apart from metals and non-metals some elements show properties of both metals and non –metals,e.g. Silicon, Arsenic, Germanium .They are called metalloids.Comparison of physical and chemical properties of metals and non – metals:-Property Metals Non-Metals1 Physical State Metals are solid at room temperature. Except mercury and gallium.Non-metals generally exist as solids and gases, except Bromine.2 Melting and boiling points Metals generally have high m.pt and b.pt except gallium and cesium. Non-metals have low m.pt and b.pt except diamond and graphite. 3 Density Generally high. Generally low.4 Malleability and Ductility Malleable and ductile. Neither malleable nor ductile.5 Electrical and thermal conductivity Good conductors of heat and electricity.Generally poor conductors of heat and electricity except graphite. 6 Luster Poses shining luster. Do not have luster except iodine.7 Sonorous sound Give sonorous sound when struck.Does not give sonorous sound.8 Hardness Generally hard except Na, K Solid non-metals are generally soft except diamond.Comparison of Chemical Properties of Metals and Non-metals:-1 Reaction with OxygenMetal + Oxygen Metal oxide4Na(s) + O2(g)  2Na2O(s)4Al(s) + 3O2(g)  2Al2O3Metals form basic oxides Zn and Al form amphoteric oxides (they show the properties of both acidic and basic oxides) Most of the metal oxides are insoluble in water Some of them dissolve to form Alkali Na2O(s) + H2O(l)  2NaOH(aq)Non-metal + Oxygen  Non-metal oxide C +O2  CO2S + O2  SO2Non-metals form acidic oxides CO and H2O are neutral oxides(they are neither acidic nor basic innature) Non-metal oxides are soluble in waterThey dissolve in water to form acids SO2 + H2O  H2SO32 Reaction with waterMetals react with water to form metal oxides or metal hydroxide and H2 gas is released. 2Na(s) +2H2O(l)  2NaOH + H2(g) + heatNon-metals do not react with water, steam to evolve hydrogen gas.Because Non-metals cannot give electrons to hydrogen in water so that it can be released as H2 gas.3 Reaction with dilute AcidsMetal + Acid  Metal salt + Hydrogen2Na(s) + H2SO4  Na2SO4(aq) +H2(g) HNO3Metal + HNO3  H2 gas is notdisplaced.Reason- HNO3 is strong oxidizing agent.Non-metals do not react with acids to release H2 gasReason- Non-metals cannot loose electrons and give it to Hydrogen ions of acids so that the gas isreleased.Mn + 2HNO3  Mn(NO3)2 + H2H2 gas from HNO34 Reaction with salt solutionsWhen metals react with salt solution, more reactive metal will displace a less reactive metal from its salt solution.CuSO4(aq) + Zn(s)  ZnSO4(aq) + Cu(s)When non-metals react with salt solution, more reactive non-metal will displace a less reactive nonmetal from its salt solution.2NaBr(aq) + Cl2(g)  2NaCl(aq) + Br2(aq)5 Reaction withChlorineMetal + Chlorine  Metal Chlorideionic bond is formed. Therefore Ionic compound is obtained. 2Na + Cl2  2NaClNon-metal + Chlorine  Non-metalChloride covalent bond is formed. Therefore covalent compound is obtained.H2(g) + Cl2  2HCl6 Reaction with HydrogenMetals react with hydrogen to form metal hydride This reaction takes place only for mostreactive metals. 2Na(s) + H2(g)  2NaH(s)Non-metals react with hydrogen to form hydrides H2(g) + S(l)  H2S(g)Properties of ionic compounds1. Physical nature:solid and hard due to strong force of attraction. (generally brittle)2. Melting point and boiling point:have high M.P and B.P, as large amount of heatenergy is required to break strong ionic attraction.3. Solubility: soluble in water and insoluble in kerosene and pertrol.4. Conduction of electricity:ionic compounds in solid state-----does not conductelectricity.Reason—Ions can not move due to rigid solid structure. Ionic compounds conductelectricity in molten state.Reason-- Ions can move freely since the electrostatic forces of attraction between theoppositely charged ions are overcome due to heat.Occurrence of metals.It occurs in Earths crust, sea-waterElements or compounds, occuring naturally Minerals that contain very high percentagein the earth‘s crust of a perticular metal and these metals can beextracted economically on a large scale.e.g Bouxite ore → AluminiumHaematite → IronMinerals OresSUGGESTED ACTIVITIES1. Testing physical properties of metals2. Metals are good conductor of heat3. Metals are good conductor of electricity4. Testing chemical properties of metals5. To show properties of ionic compound6. Investigating the conditions under which iron rustedHOTS QUESTIONS (SOLVED / UNSOLVED)Q.1 a) What are amphoteric oxides? Choose the amphoteric oxides from amongst the following:Na2O, ZnO, Al2O3, CO2, H2Ob) Why is it that non metals do not displace hydrogen from dilute acid?Ans. a) The oxides which are acidic as well as basic in nature are called amphoteric oxides. ZnO andAl2O3are amphoteric oxides.b) Non metals can not loose electrons so that H+ ions become hydrogen gas.Q.2. What is anodizing? What is its use?Ans. The process of forming thick oxide layer of aluminium oxide that makes it resistant to furthercorrosion.Q.3. What is Aqua regia? What is its use?Ans. It is a mixture of concentrated HCl and concentrated HNO3 in the ratio 3:1. It can dissolve goldand platinum.Q.4. Give reason: Aluminium is highly reactive metal, but it is used to make utensils for cooking.Q.5. Explain why (a) Iron articles are frequently painted. (b) Iron sheets are coated with Zinc layer.Q.6 On adding dilute HCl acid to copper oxide powder, the solution formed is blue – green. Predictthe new compound formed which imparts a blue – green colour to the solution? Write itsequation.Q.7. Name the property of metal used in the following cases- (i) Aluminium foil (ii) Meta jewellery(iii) Cable wires (iv) BellsQ.8. How can you prove that Zinc is more reactive than Copper?Q.9. Draw and explain the electrolytic refining of impure Copper.Q.10. Why is Aluminium extracted from Alumina by electrolytic reduction and not by reducing it withCarbon?Q.11 Write 3 points of difference between Calcination & Roasting?Q.12 Write 5 points of difference between Ionic compound and covalent compound.Q.13 What is thermit reaction? Give its one use.Q.14 What is amalgam?Q. 15 Magnesium when reacts with hot water, starts floating. Why?Chemistry for class 10....acids-and-alkaliscarbon-and-its-compound-notesperiodic-classification-of-elementsunsaturated-hydrocarbonmetal-and-non-metals-noteschemical-reaction-and-equations-notes-2periodic-classification-of-elements